Cylinders for gas under pressure are conventionally cylindrical in shape, with an upper shoulder through which a port passes. Valving and regulating devices are attached to threads at this port, and extend beyond the cylinder itself where they are exposed to the risk of physical damage by impact. In transit, caps are screwed onto the shoulder to protect anything attached to the port, and are generally satisfactory.
However, when the caps are removed, and sometimes even when they are in place, impact forces may be exerted, perhaps from dropping the cylinder, which could damage the valves and permit the confined gases to escape. The situation is bad enough when non-toxic gases are involved, although in these situations there still exists the potential problem of jet-like movement of the cylinder due to impulse of the escaping gases. But when toxic gases are involved, such as arsine or other gases used in the semi-conductor industry, escape of the gases can lead to catastrophic consequences.
It is an object of this invention to provide a safety shutoff valve which is normally open, but when it is distorted, immediately closes the port from the gas cylinder. Thus, whatever may have happened to it or to any downstream controls directly attached to it, the gas cylinder will be shut off from leakage.